Copyright ©ERS Journals Ltd 1998 European Respiratory Journal

for the Canadian and the Dutch Formoterol Investigators aa Measurement of quality of life (QoL) is increasingly being used in clinical intervention studies and has been shown to be a valid indicator in assessing whether a medi-cal treatment is beneficial [1–4]. The assessment of QoL is now regarded as being one of the main outcome varia-bles in clinical studies [5, 6], especially in chronic dis-eases such as asthma, in which a cure by medical intervention is seldom achieved. In this respect, QoL is referred to as the daily functioning and the subjective wellbeing of the pat-ient. Although asthma-specific QoL questionnaires have been developed only recently, the number of trials in which QoL measurement has been applied is growing rapidly